add feature to docs

docs/how-to/backup-your-databases.md

@@ -231,7 +231,8 @@ If you have a single repository in your borgmatic configuration file(s), no
 problem: the `restore` action figures out which repository to use.
 
 But if you have multiple repositories configured, then you'll need to specify
-the repository path containing the archive to restore. Here's an example:
+the repository to use via the `--repository` flag. This can be done either
+with the repository's path or its label as configured in your borgmatic configuration file.
 
 ```bash
 borgmatic restore --repository repo.borg --archive host-2023-...

docs/how-to/extract-a-backup.md

@@ -51,7 +51,8 @@ If you have a single repository in your borgmatic configuration file(s), no
 problem: the `extract` action figures out which repository to use.
 
 But if you have multiple repositories configured, then you'll need to specify
-the repository path containing the archive to extract. Here's an example:
+the repository to use via the `--repository` flag. This can be done either
+with the repository's path or its label as configured in your borgmatic configuration file.
 
 ```bash
 borgmatic extract --repository repo.borg --archive host-2023-...

docs/how-to/run-arbitrary-borg-commands.md

@@ -53,7 +53,8 @@ This runs Borg's `rlist` command once on each configured borgmatic repository.
 (The native `borgmatic rlist` action should be preferred for most use.)
 
 What if you only want to run Borg on a single configured borgmatic repository
-when you've got several configured? Not a problem.
+when you've got several configured? Not a problem. The `--repository` argument
+lets you specify the repository to use, either by its path or its label:
 
 ```bash
 borgmatic borg --repository repo.borg break-lock